Why a flat rate is usually wrong
A single flat shipping fee at checkout is the fastest thing to set up on a new Shopify store, and it is wrong for most orders that pass through it. Set the flat rate to cover a heavy order and every light order subsidises shipping it did not need. Set it to suit the light orders and heavy ones start costing the business money on every sale. Neither version reflects what NZ Post actually charges, because that number moves with weight, dimensions and destination.
How live rates actually work
NZ Post moves a significant share of parcels for New Zealand ecommerce businesses, and Shopify can be connected to it either directly or through a shipping app, depending on order volume and whether other couriers are already in use. Done properly, the connection pulls a live rate at checkout based on the actual weight and destination of the cart, so a customer buying one small item and a customer buying a full box see different, accurate numbers instead of the same flat guess.
Rural delivery is where most default setups fall over. NZ Post applies rural surcharges and different timeframes to a meaningful share of New Zealand addresses, and a checkout that has not been configured to reflect that either absorbs the cost without saying so or surprises a rural customer with a charge that was not shown until the order confirmation. Neither outcome is good, and both are avoidable with the right configuration from the start.
Direct connection versus a shipping app
A store shipping low volumes through NZ Post alone can often connect directly. A store running NZ Post alongside two or three other couriers usually gets more consistent results through a shipping app like Starshipit or Go Sweet Spot, which can compare NZ Post against other options and choose automatically rather than defaulting to one courier regardless of fit. Which approach makes sense depends on order volume and how many courier relationships a business already has.
What the setup needs to get right
Labels should generate from the order data itself, address and parcel details flowing straight from Shopify rather than being re-typed by a warehouse team under time pressure. Tracking should reach the customer automatically the moment a parcel is dispatched, since a tracking email sent on time removes most of the where-is-my-order enquiries before they are written. We scope the right connection for a given order volume and manage the setup so rates, rural rules and tracking all match how NZ Post actually charges and delivers, tested against real orders before it carries a live customer's parcel.
